<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>low计算器</title>
</head>
<body>
<input type="text" id="i1">
<input type="text" id="i2">
<input type="button" value="加" onclick="f(1)" id="i3">
<input type="button" value="减" onclick="f(2)" id="i4">
<input type="button" value="乘" onclick="f(3)" id="i5">
<input type="button" value="除" onclick="f(4)" id="i6">
<div>结果：<b></b></div>
<script>
    function f(x) {
        let i1 = document.querySelector("#i1");
        let i2 = document.querySelector("#i2");
        let b = document.querySelector("b");
        if (isNaN(i1.value) || isNaN(i2.value)) {
            b.innerText = "输入错误";
            return;
        }
        switch (x){
            case 1:
                b.innerText = i1.value*1 + i2.value*1;
                break;
            case 2:
                b.innerText = i1.value - i2.value;
                break;
            case 3:
                b.innerText = i1.value * i2.value;
                break
            case 4:
                b.innerText = i1.value / i2.value;
        }
    }
</script>

</body>
</html>